1. Field of the Invention
This invention pertains to transfer truck and trailer sets and more particularly to a comprehensive system for securing the tailgates of the truck and trailer bodies on a selective basis and for retaining the trailer body in the truck body for tilting therewith to empty contents from the trailer body.
2. Background Art
The development of transfer truck and trailer sets has improved dramatically the capacity to transport and discharge the large volume of materials commonly associated with activities such as excavation, civil construction, mining, and demolition. In such a transfer set, the transfer truck, which has a body capable of tilting on the truck frame in the manner of a dump truck, is used in addition to tow a trailer. The trailer is provided with a body capable of being separated from the trailer frame then being entered into the truck body for tiling therewith.
By the use of this combination of equipment, the volume of material that can be transported and handled by a single truck operator attendant to activities such as those named above is substantially enhanced. The number of trips required to transport materials can be reduced, saving time and resulting in a corresponding reduction in the number of motorized vehicles required for any given project.
Nevertheless, impediments remain to fully realizing the potential benefits of a transfer truck and trailer set. In addition, such sets continue to exhibit a need to adequately preserve the safety of operators.
One such area of as yet unsatisfactory development relative to transfer truck and trailer sets relates to the manner in which the trailer body when received into the truck body is secured therein for tilting therewith. Previously a bar was fixed across the width of the truck above and at the front of the truck body. The bar was capable of being engaged by spring-loaded hooks secured to the front upper end of the trailer body as it was received fully into the truck body. Once the truck body with the trailer body secured therein had been tilted to empty contents from the trailer body, it was necessary in using such a securement system for the operator of the transfer set to climb to the top of the truck body and pivot the bar out of engagement with the hooks. This permitted the trailer body thereafter to be removed from the truck body to the trailer frame.
In the process described, the quality of trailer body securement achieved was relatively acceptable. The weight of the trailer body and its contents remained stable in the truck body during movement and tilting, and the wheels on the bottom of the trailer body infrequently came off of the rails installed in the floor of the truck body to support the trailer body.
Nevertheless, because the approach required operator access to latching mechanisms at the top of the truck body, the release of such mechanisms proved to be time consuming and inconvenient. Typically, the control of mechanism for withdrawing the trailer body from the truck body are located on the outside of the truck body toward the rear thereof at a point accessible by an operator from the ground. Accordingly, after having released the bar retaining the trailer body in the truck body, the operator was required to climb down from the top of the truck body and move on the ground to the rear of the truck body for the purpose of operating the control mechanisms by which to return the trailer body to the trailer frame.
If the transfer truck could not be parked on a very level surface during this operation, serious dangers were presented also. Once released from the truck body, the trailer body could begin to slide rearwardly without any control whatsoever out of the truck body. The longer such sliding was permitted, the more severe would be the consequences. Knowing this, operators tended to rush from the top of the transfer truck to the position at which control mechanisms for movement of the transfer trailer body could be accorded. Such haste also produced its own dangers.
Accordingly, an alternative approach to securing a transfer trailer body in a transfer truck body was undertaken. To eliminate the need for the operator of the set to climb to the top of the truck body, a cooperating latching mechanism for the trailer body was developed and placed at the bottom rear of each of the bodies of the truck and trailer. Spring-loaded hooks were secured at a low position on both sides of the truck body so as to capture retention pins on the outside and at the rear of the trailer body. A torsion bar to passing under the opening to the truck body permitted an operator at one side of the truck to release both hooks when it was desired to transfer the trailer body out of the truck body. While more convenient than the method described earlier, this approach presented drawbacks in other areas.
First, because the site of securement of the trailer body to the truck body in such an approach was at a lower rear location thereon, the trailer body and its contents were observed to have a tendency to pivot about the attachment site. This permitted the front end of the trailer body to rise inside the truck body and derail the wheels on the bottom of the trailer body from the rails upon which those wheels are designed to ride.
Securement of the trailer body at a low position in the rear of the trailer body afforded inadequate restraint on vertical movement of the trailer body. Thus, it was relatively frequent that after routine job-site jostling, a derailed trailer body could not be removed from its truck body. As a solution, various systems of interlocking horns and apertures on the outside of the trailer body and the inside of the truck body were devised, but these complicated the design and increased the cost of manufacturing the set.
Spring-loaded hooks at the bottom rear of the truck body are also dangerous to the operator the transfer set. The ready accessibility of the release mechanism utilized with this type of latching system led to its inadvertent activation on a regular basis. When this would occur, disengagement of the trailer body from the truck body was the result, with substantial corresponding injury and property damage. This risk was most severe when the truck body with the trailer body secured therein was in a tilted position.
In response, such latching systems were enhanced by incorporating a variety of safety pins thereinto which were designed to prevent thoughtless activation of the detachment mechanism. Nevertheless, the objective of such pins could also be defeated by thoughtlessness. Each required conscious operator action to effect installation for the time that the trailer body was to be retained in the truck body. Accordingly, normal forgetfulness and ingenious corner-cutting on the part of operators continued to preserve the opportunity for inadvertent trailer body detachment.
A closely related aspect of transfer trailer truck set operation which has yet received serious attention relates to the latching and unlatching of the tailgates associated with each of the truck and trailer bodies. In order to avoid exposing the operator to the dangers presented when the truck tailgate was first released, systems were devised by which to permit the operator to release the truck tailgate from inside the cab. Such systems were pneumatically or electro-mechanically affected. Nevertheless, little attention has been paid to the problem of keeping the tailgate on the trailer body securely latched until such time as the contents of the trailer body are to be emptied, or thereafter to afford the operator of the transfer set the same measure of safety as has been a long standing concern relative to the initial opening of the tailgate of the truck.
Thus, the design and construction of vehicles has been wanting with respect to efficiency, safety, and convenience relative to the operation commonly encountered in the use of truck and trailer transfer sets.